For decades, scientists have attempted to find the perfect artificial heart valve, since the valve could impact the health of thousands of people in the United States alone. Continuous improvement of prosthetic heart valves has been performed since 1953 when Hufnagel performed successful implantation of a prosthetic human valve [1]. In the 1990s it is estimated that 20000 people die each year as a result of valvar dysfunction, and 60000 valve replacement operations are performed annually in the United States [2]. The number of procedures is expected to grow as the outcome of operations for patients with congenital heart disease continues to improve with growth of these individuals into adulthood. Currently available options include biologic valves and mechanical valves, both of which have significant drawbacks: mainly durability and anticoagulation-related issues, respectively. Native heart valves are biologically active tissues that survive well throughout an individual's life, opening and closing over 3 billion times in the average human lifetime. The optimum heart valve replacement should be competent, have a low opening pressure, be durable, not require anticoagulation therapy, have potential for growth, and not induce host reactions to the valve material. Attempts to manufacture the “ultimate” valve have failed to date.
Current options for valve replacement include mechanical valves, tissue engineered valves, animal and human graft valves. Patients with mechanical valves must have daily blood anticoagulation treatments. For tissue heart valves, availability for human use is a paramount concern as well as limited longevity due to host reaction to the valve material with calcification, disintegration and failure of the valve mechanism leading to stenosis and/or incompetence.
The use of polymeric heart valve prostheses dates back to the 1950s, and numerous biomaterials (including silicone, polytetrafluoroethylene (PTEF), and polyurethane (PU)) have been tested as leaflet materials [3]. Unfortunately, after many years of experience, problems associated with polymeric heart valve prostheses have not been completely eliminated, demonstrating that none of the developed valves are ideal for replacement procedures [4]. It has been reported that silicone rubbers have been abandoned due to their poor flexural fatigue life, which result from work hardening of the material caused by the cyclic opening and closing of the valve [5, 6]. The tested PTFE and PU valves exhibited abrasive wear associated with calcification and eventually failed [3, 7].